As a material for a holographic recording medium, for example, compositions for optical recording have been proposed in which a photopolymer is filled into a film of an inorganic glass network, as disclosed in the publications of Japanese Patent Nos. 2953200 and 3039165. Further, various materials have been proposed as the abovementioned photopolymer.
In the invention of the abovementioned patent publications, a holographic recording medium is configured by sandwiching a hybrid material or a photopolymer between a pair of glass substrates.
For the holographic recording medium as mentioned above, the thicker a recording layer, the better as a volume type holographic recording medium. However, the formation of a thick film of the abovementioned hybrid material or photopolymer is technologically difficult, and there arise problems such as scattering due to uneven thickness and nonuniformity of remaining dynamic range (to be described hereinafter).
Moreover, it is conceivable that multiple layers of the above material may be laminated to configure a thick recording layer. However, in this case, the number of manufacturing steps increases to cause a problem that manufacturing cost increases.